'use strict';

function calculate_elements_sum(collection, element) {
  //在这里写入代码
  // return collection.IndexOf(element);
  var res;
  for (var i =0 ; i<collection.length ; i++){
    if(collection[i] === element){
      res = i ;
      break;
    }
  }
  return res;
}

module.exports = calculate_elements_sum;

